Integrated circuits are typically formed on semiconductor chips. To increase manufacturing throughput and lower manufacturing cost, the integrated circuits are manufactured in semiconductor wafers, each containing many identical semiconductor chips. After the integrated circuits are manufactured, semiconductor chips are sawed from the wafers and packaged before they can be used.
In some packaging processes, semiconductor chips (also referred to as dies in the art) are bonded to package substrates. Underfill, which typically comprises epoxy, is used to further secure the bonding. The semiconductor chips may be bonded using flip-chip bonding or wire bonding. In the flip chip bonding process of a die to a package substrate, a re-flow process is performed so that the solder between the die and the package substrate is melted to join the die to the package substrate.
The conventional bonding process suffers from drawbacks. For example, during the re-flow process, the temperature of the package substrate is elevated. Since the package substrate is prone to warpage, after the reflow, package substrate may have warpage. With the warpage of the package substrate, the bumps at the center and the edges of the die and/or the package substrate are stretched or compressed. This causes stresses to be imparted to the low-k dielectric materials in the die, and delamination may occur to the low-k dielectric layers. In addition, the stresses may further cause the solder between the die and the package substrate to suffer from cracking.